Alexander Dennis submitted a model Enviro 500, diesel-powered 79 seat (including the driver) 42-foot bus, for a partial STURAA test in the 12 yr/500,000 mile test category.  The Federal Transit Administration determined that the following tests would be performed:  1.2 and 1.3 of Maintainablity, 2. Reliability, 4. Performance, 5.7 Structural Durability, 6. Fuel Economy, conditions 1 and 2 of 7. Interior Noise test and 7.1 Exterior Noise Test.  Testing started on November 28, 2007 and was completed on May 9, 2008.  The Check-In section of the report provides a description of the bus and specifies its major components.

 The primary part of the test program is the Structural Durability Test, which also provides the information for the Maintainability and Reliability results.  The Structural Durability Test was started on December 10, 2007 and was completed on April 22, 2008.

The interior of the bus is configured with seating for 32 passengers including the driver on the lower level and 47 passengers on the upper level.  Free floor space will accommodate 37 standing passengers on the lower level resulting in a potential load of 116 persons.  At 150 lbs per person, this load results in a measured gross vehicle weight of 55,850 lbs.  In order to avoid exceeding the GAWR of all three axles, ballast for all 37 standing passengers was eliminated.  This reduction from full capacity resulted in an adjusted measured gross vehicle weight of 50,120 lbs and was used for all dynamic testing.  The first segment of the Structural Durability Test was performed with the bus loaded to a GVW of 50,120 lbs.  The middle seated load weight segment was performed at the same 50,120 lbs and the final segment was performed at a curb weight of 37,930 lbs.  Durability driving resulted in unscheduled maintenance and failures that involved a variety of subsystems.  A description of failures, and a complete and detailed listing of scheduled and unscheduled maintenance is provided in the Maintainability section of this report.

 Accessibility, in general, was adequate, components covered in Section 1.3 (Repair and/or Replacement of Selected Subsystems) along with all other components encountered during testing, were found to be readily accessible and no restrictions were noted.            

 The Reliability section compiles failures that occurred during Structural Durability Testing.  Breakdowns are classified according to subsystems.  The data in this section are arranged so that those subsystems with more frequent problems are apparent.  Also the problems also are listed by class as defined in Section 2.  The test bus encountered no Class 1 or Class 2 failures.  Of the thirty-seven reported failures, 28 were Class 3 and 9 were Class 4.

 The performance of the bus is illustrated by a speed vs. time plot.  Acceleration and gradeability test data are provided in Section 4, Performance.  The average time to obtain 50 mph was 39.62 seconds.


A Fuel Economy Test was run on simulated central business district, arterial, and commuter courses.  The results were 2.69 mpg, 3.00 mpg, and 5.72 mpg respectively; with an overall average of 3.28 mpg.

 A series of Interior and Exterior Noise Tests was performed.  These data are listed in Section 7.1 and 7.2 respectively.

Number: 0712-P
Model: ENVIRO 500
Vin Number: SFET455257GN11888